How often should you change your furnace filter?

Common guidelines

These are typical ranges. The filter packaging and your system's manual have the final say.

• Thin 1-inch filters: often every 1–3 months.
• Thicker 4–5 inch media filters: often every 6–12 months.
• Washable filters: clean on the schedule the manufacturer gives.

Change it more often if…

• You have pets that shed.
• Someone in the home has allergies or asthma.
• There's renovation dust, wildfire smoke or heavy pollen.
• The heat or air conditioning is running most of the day.

Signs it's overdue

• The filter looks grey and you can't see light through it.
• More dust settles on furniture than usual.
• Rooms take longer to heat or cool.
• Your energy bill creeps up with no other explanation.

Before you buy a replacement

Write down the exact size printed on the filter's edge (for example 16×25×1) and the rating, so you buy the right one every time.